When I cruise on the interstate on a flat grade, either loaded or unloaded, my CTD is very very quiet. When I'm pulling my 11K 5er, and hit a hill, my engine will become quite noisy if I'm pushing it until I crest the hill. I know this is normal, but what is causing the noise? I would characterize the noise as a mechanical rattle! It is just my curriousity and desire to learn, that results in the question!

 

I think you are hearing the injectors. If I drive, I tend to hear the injectors. When my wife drives, I tend to hear the turbo more.

 

Could it be the normal diesel noise like a non-pilot injected diesel would make? Maybe the pilot injection goes off with too much throttle or just can't stop the noise at higher throttle settings.